Milk powder ex factory is most often packed in multiwall bags ranging from 10-30 kg, but typically 25 kg in weight that have a multilayer brown (Kraft) paper outer bag for handling strength and a plastic inner liner for powder containment. The bags are sealed using a heat sealer that acts through the paper bag to seal the inner plastic liner. The paper bag is sealed by folding its protruding flap over and re-heating hot melt glue on the underside of the flap. A line of cuts/perforation is scored along the inside of the plastic liner bag to assist separation of the plastic liner from the outer paper bag when this is required. When the bags are constructed, small traces of hot-melt glue are used to fix the inner plastic liner to the outer paper bag in order to assist filling the bag with powder in an automated process.
In order to comply with hygiene requirements, hygienic recovery of the bag contents is required before the product can be further processed into for example infant formula, retail packs or the like. The outer bag which may be contaminated must be removed in a way that maintains the cleanliness of the inner plastic liner bag.